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Terrain Analysis

This tutorial derives terrain products from a digital elevation model (DEM): a hillshade, a slope map, and contour lines. It uses the Raster tools under Processing → GeoLibre Toolbox → Raster.

Which engine runs these

Hillshade, Slope, and Aspect each offer a Client (browser) engine, so this tutorial's first three steps work in the browser build with nothing installed. Contour and Clip by mask layer have no client engine and need the rasterio Python sidecar, which the desktop app manages — see Getting Started. The engine picker at the top of each tool shows what is available; prefer the sidecar for large rasters or for terrain in a geographic CRS.

1. Load a DEM

Add an elevation raster as a layer, for example a GeoTIFF or COG DEM (see Adding Data). The raster tools take a file path in and write a file path out, so a local or accessible raster works best.

2. Hillshade

  1. Open Processing → GeoLibre Toolbox → Raster → Hillshade.
  2. Choose the DEM as input and set the azimuth, altitude, and z-factor if you want to adjust the lighting.
  3. Run it. The shaded-relief raster is added to the map. Place it under your other layers and set the top one's blend mode to Multiply, which lets the relief show through the colour instead of washing both out the way lowered opacity would.

3. Slope and aspect

  • Processing → GeoLibre Toolbox → Raster → Slope computes steepness from the DEM.
  • Processing → GeoLibre Toolbox → Raster → Aspect computes the compass direction of the steepest slope.

Run either against the DEM and style the output with a colormap. Open the Colorbar from the Controls menu to show the value scale.

4. Contours

  1. Open Processing → GeoLibre Toolbox → Raster → Contour.
  2. Choose the DEM and set the contour interval (the elevation difference between lines).
  3. Run it to generate contour lines as a vector layer, which you can label and style like any vector data.

Contour runs on the sidecar only, so this step needs the desktop app.

5. Clip to an area of interest

To restrict outputs to a study area, use Processing → GeoLibre Toolbox → Raster → Clip by extent (a bounding box, which also runs in the browser) or Clip by mask layer (a vector mask, sidecar only). See Processing Tools.

Next steps

  • Convert raster outputs to vectors with Polygonize, or write a Raster to COG for sharing. See Cloud-Native Data.
  • Animate a time series of rasters with the Time Slider plugin. See Data Integrations.